Temperature-insensitive fiber optic Fabry-Perot interferometer based on special air cavity for transverse load and strain measurements

We experimentally demonstrate transverse load and strain sensing based on a fiber optic Fabry-Perot interferometer (FPI) with special air cavity, which was created by fusion splicing single mode fiber (SMF), hollow core fiber (HCF) and several electrical arc discharges. The cavity height of this structure is higher than the cladding diameter of SMF so that it can sense transverse load with high sensitivity. The transverse load sensitivity of this air cavity FPI sensor is 1.31 nm∕N and about 5 times more sensitive compared to the current fiber tip interferometer (0.2526 nm∕N). Meanwhile, this sensor also can measure strain and the strain sensitivity of 3.29 pm∕με is achieved. In addition, the low temperature sensitivity (1.08 pm/°C) of the sensor can reduce the temperature-induced measurement error. This novel air cavity FPI can be developed and used as high-sensitivity transverse load and strain sensor with temperature-insensitive.